36 TERTIARY INSECTS OF NORTH AMERICA. 



But later, after a more careful revision, drawn from more extended sources, 

 he writes that while, by the presence of many genera, " there is an evident 

 relation of the Florissant flora with that of the European Miocene, yet by 

 the affinities and even identity of some of the species with those of the flora 

 of the gypsum of Aix, which, according to Saporta, includes types related 

 to those of the whole extent of the Tertiaries from the upper Cretaceous to 

 the Oligocene and abo ve, 1 should rather refer this group to the lower Mio- 

 cene or Oligocene." 



Both Lesquereux and Cope agree in placing the Florissant beds at the 

 same horizon as those of Elko, Nevada, and also those directly above the 

 Fish-cut beds at Green River, Wyoming. Lesquereux has identical species 

 also from White River, Colorado, among specimens communicated by Mr. 

 Denton. Cope calls the Florissant and Elko deposits the Amyzon beds, 

 from the prevalence of that type of fish, and refers them to the "later Eocene 

 or early Miocene." Mr. Clarence King places the Green River deposits in 

 the middle Eocene, but considers the Elko deposits of the same age. We 

 may therefore provisionally conclude, from the evidence afforded by the 

 plants and vertebrates, that the Florissant beds belong in or near the Oli- 

 gocene. 



At present no geological conclusions can be drawn from what is known 

 of the insects. So far as specific and generic determinations has proceeded, 

 scarcely anything identical has been found in the Green River and Floris- 

 sant beds, but some remarkable affinities have been noticed. To attempt, 

 however, to draw any conclusion as to the age of either of these deposits, 

 and especially of th;it of Florissant, before a closer examination is made 

 would be folly. Almost the entire series of fossil insects from the beds of 

 Aix, Oeningen, and Radoboj requires a careful generic revision, and until 

 this is done it will be difficult to make much use of the information given 

 us in the works of European authors. This should not be considered as 

 reflecting upon the character of these works, for it must be remembered 

 that they were nearly all completed thirty years ago and could not be 

 expected to meet present demands. It is, indeed, probable that the richer 

 American fields, the exploitation of which has only just begun, may yet be 

 found the best basis for the study of the relationship of the Tertiary insect 

 faunas of Europe. 



White River. Fossil insects were first discovered on the lower White 

 River in western Colorado and eastern Utali by Mr. William Dentou during 



